1. Field of the Invention
The present invention relates to an electronic cassette and an electronic cassette system for use in radiography.
2. Description Related to the Prior Art
An electronic cassette has been widely used in medical radiography, for example, in X-ray photography. An electronic cassette system includes an electronic cassette. The electronic cassette is a portable X-ray image detector provided with an built-in image detector (also referred to as flat panel detector (FPD)) for detecting an X-ray image of a subject such as a patient inside a housing having a front surface on which X-rays are incident, a rear surface facing the front surface, and four side surfaces.
The electronic cassette is set to be attachable to and detachable from a holder of an upright radiographic stand or a supine radiographic stand such that the electronic cassette is held in a posture in which an X-ray source for irradiating X-rays and the front surface of the housing face each other. Further, the electronic cassette is used alone for a subject lying on a bed or a subject who cannot move on his/her own such as an aged person or an emergency patient in some cases, in addition to being set to the holder of the upright radiographic stand or the supine radiographic stand.
Further, in X-ray photography, since scattered rays are generated upon transmission of X-rays through a subject, a grid for removing the scattered rays is used in some cases. There is a grid detachably attached to an electronic cassette externally (hereinafter referred to as external grid) (see Utility Model Registration No. 3137548 and Utility Model Registration No. 3144690). In the case where the electronic cassette is used alone, the outer grid is attached to the electronic cassette.
The external grid consists of a grid body and a holding frame for holding the grid body. The grid body is attached to the holding frame. The holding frame has a top panel for covering the front surface of the housing, and a side panel which is provided to an edge of the top panel and extends in a direction from a front-surface side to a rear-surface side of the housing so as to cover part of the side surface of the housing.
As shown in FIG. 1 of Japanese Patent Laid-Open Publication No. 2013-033055, an electronic cassette includes an indicator. The indicator functions to inform an operator such as a radiation technologist of operation conditions of the electronic cassette such as power on/off of the electronic cassette and whether or not preparation for detecting an X-ray image by an image detector has been completed, or a center position of each side of a rectangular imaging area of the image detector which serves as a mark in X-ray photography. The indicator includes a light source disposed inside a housing, and a display window disposed on an outer surface of the housing through which light from the light source is emitted to the outside. Utility Model Registration No. 3137548 discloses an LED (Light Emitting Diode) as a light source and a display window having a L-shape which is formed to extend from a side surface to a front surface of a housing.
However, in the case where the display window is formed on the side surface or the front surface of the housing as disclosed in Utility Model Registration No. 3137548, when the outer grid is attached to the electronic cassette, the display window is covered by the outer grid, and there arises a problem that it becomes impossible for an operator to check a display state of the indicator.
Further, even in the case where the outer grid is not attached to the electronic cassette, when the electronic cassette is inserted into a clearance between a subject and a mounting surface of a bed or the like on which the subject is lying, in particular, the display window formed on the front surface of the housing is covered by the subject, and there arises a problem that it becomes impossible for an operator to check a display state of the indicator.